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Regulatory matters - NDPSC (Details) - NDPSC - Montana-Dakota Utilities Co.
$ in Millions
Nov. 01, 2024
USD ($)
Dec. 13, 2023
USD ($)
Nov. 01, 2023
USD ($)
Sep. 16, 2024
USD ($)
Public Utilities, General Disclosures [Line Items]        
Public utilities, annual revenue increase (decrease)       $ 9.4
Public utilities, annual revenue increase (decrease), percentage       0.061
Natural gas distribution | Pending Rate Case        
Public Utilities, General Disclosures [Line Items]        
Public utilities, requested rate increase (decrease), amount     $ 11.6  
Public utilities, requested rate increase (decrease), percentage     7.50%  
Public utilities, interim rate increase (decrease), amount   $ 10.1    
Public utilities, interim rate increase (decrease), percentage   6.50%    
Electric | Subsequent Event        
Public Utilities, General Disclosures [Line Items]        
Requested renewable resource cost adjustment rate tariff $ 18.3      
Public utilities, approved rate increase (decrease), amount $ 2.8